1. Field of the Invention
The present general inventive concept relates to a side emitting device, a backlight unit using the same as a light source, and an image display apparatus employing the backlight unit.
2. Description of the Related Art
Liquid crystal displays (LCDs), a type of flat panel display, are light receiving displays in which an image is produced not by self-emission but by external light. The LCDs need external light sources to display images since the LCDs themselves do not directly emit light. When using LCDs, backlight units are installed at a rear side of the LCDs to illuminate the LCDs.
The backlight units are mainly classified according to the arrangement of the light sources into a direct light type, in which a plurality of light sources are installed behind an LCD to directly emit light onto a liquid crystal panel, and an edge-light type, in which a light source is installed at a sidewall of a light guide panel (LGP) propagating light toward a liquid crystal panel.
The direct light type backlight units may use a light emitting diode (LED) that emits a Lambertian light as a point light source. When the light emitted from the LED is diffused by a diffusion plate and then directed onto a liquid crystal panel, in order to make color light emitted from the LED not noticeable over the diffusion plate, a side emitting LED that can change the direction of the light from the LED in a side direction, such that the light is incident onto the diffusion plate is required.
U.S. Pat. No. 6,679,621 discloses a side emitting LED. The conventional side emitting LED of U.S. Pat. No. 6,679,621 includes a funnel-shaped reflecting surface obliquely angled with respect to a central axis, a first refracting surface obliquely angled with respect to the central axis and refracting light reflected by the reflecting surface, and a convex or sawtooth-shaped second refracting surface extending from a bottom surface to the first refracting surface.
Light emitted from the light source and directly incident on the funnel-shaped reflecting surface is then reflected by the reflecting surface to the first refracting surface, where it is then refracted thereby by the first refracting surface to propagate substantially sideways. Light emitted from the light source and directly incident on the convex second refracting surface is refracted by the second refracting surface to propagate substantially sideways.
Since the conventional side emitting LED emits light sideways, when the conventional side emitting LEDs are arranged in an array, adjacent LEDs may interfere with each other. Accordingly, the conventional side emitting LED is not suitable for backlight units.